Liquid supply system

ABSTRACT

A liquid supply system that enables a reduction in time required for precooling to reduce the time taken to make a pump operable. A container  130  includes a first casing  131  in which fluid passages passing through a first pump chamber P 1  and a second pump chamber P 2  are provided and a second casing  132  that surrounds the outer wall of the first casing  131 . A space (fourth space K 4 ) between the first casing  131  and the second casing  132  is configured to allow a cryogenic liquid for precooling to flow through it.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2018/003630, filed Feb. 2, 2018 (now WO 2018/143419), which claimspriority to Japanese Application No. 2017-019042, filed Feb. 3, 2017.The entire disclosures of each of the above applications areincorporated herein by reference.

FIELD

The present disclosure relates to a liquid supply system used to supplycryogenic liquid.

BACKGROUND

It is known in prior art to use a liquid supply system having a pumpchamber using a bellows to cause a cryogenic liquid such as liquidnitrogen or liquid helium to circulate in a circulation fluid passage(see Patent Literatures 1 and 2 in the citation list below). In such aliquid supply system, the pump cannot operate satisfactorily if thefluid passage that passes through the pump chamber is not filled withliquid. Hence, when the system is started for the first time or when thesystem is started after maintenance, it is necessary to performprecooling so as to prevent vaporization of the cryogenic liquid in thefluid passage. To this end, before the liquid supply system is started,the cryogenic liquid is caused to flow in the fluid passage passingthrough the pump chamber to precool the fluid passage.

In conventional systems, the cryogenic liquid is caused to flow directlyin the fluid passage passing through the pump chamber. It takes a longtime to cool the fluid passage to make the pump operable by thisprocess.

CITATION LIST Patent Literature [PTL 1] WO 2016/006648 [PTL 2] WO2006/003871 SUMMARY Technical Problem

An object of the present disclosure is to provide a liquid supply systemthat enables a reduction in time required for precooling to reduce thetime taken to make a pump operable.

Solution to Problem

To achieve the above object, the following features are adopted.

An aspect of the present disclosure is a liquid supply system comprises:a container having an inlet and an outlet for cryogenic liquid andprovided with a pump chamber inside it; a shaft member that movesvertically upward and downward in the container; and a bellows thatexpands and contracts with upward and downward motion of the shaftmember; wherein the pump chamber is formed by a space surrounding theouter circumference of the bellows, the container includes a firstcasing in which a fluid passage passing through the pump chamber isprovided and a second casing configured in such a way as to surround theouter wall of the first casing, and a space between the first casing andthe second casing is configured to allow cryogenic liquid for precoolingto flow through it.

The fluid passage provided in the first casing can be precooled bycausing cryogenic liquid for precooling to flow in the space between thefirst casing and the second casing. Thereafter, the fluid passage can becooled in a short time by causing cryogenic liquid to flow in the fluidpassage. This can reduce the time taken to make the pump operable.

The space between the first casing and the second casing may be kept ina vacuum state with the cryogenic liquid having been removed from thespace between the first casing and the second casing after precooling.

With this feature, the space between the first casing and the secondcasing can provide heat insulation.

A hermetically sealed space other than the liquid supply passage passingthrough the pump chamber may be provided in the interior of the firstcasing, and the hermetically sealed space and the space between thefirst casing and the second casing may be in communication with eachother.

The system may further comprise a third casing that surrounds the secondcasing and that a hermetically sealed space kept in a vacuum state maybe formed between the second casing and the third casing.

With this feature, the hermetically sealed space between the secondcasing and the third casing can provide heat insulation.

This enables efficient cooling to be achieved when cryogenic liquidflows in the space between the first casing and the second casing.

Advantageous Effects of the Disclosure

According to the present disclosure, precooling can be performed in areduced time, and the time taken to make the pump operable can beshortened.

DRAWINGS

FIG. 1 is a diagram illustrating the general configuration of a liquidsupply system in a first embodiment.

FIG. 2 is a diagram illustrating the general configuration of a liquidsupply system in a second embodiment.

DETAILED DESCRIPTION

In the following, modes for carrying out the present disclosure will bedescribed specifically on the basis of specific embodiments withreference to the drawings. The dimensions, materials, shapes, relativearrangements, and other features of the components that will bedescribed in connection with the embodiments are not intended to limitthe technical scope of the present disclosure only to them, unlessparticularly stated.

First Embodiment

A liquid supply system in a first embodiment will be described withreference to FIG. 1. The liquid supply system is suitably used for thepurpose of, for example, maintaining a superconducting device in anultra-low temperature state. Superconducting devices require perpetualcooling of components such as superconducting coils. Thus, a cooleddevice including a superconducting coil and other components isperpetually cooled by continuous supply of a cryogenic liquid (such asliquid nitrogen or liquid helium) to the cooled device. Specifically, acirculating fluid passage passing through the cooled device is provided,and the liquid supply system is connected to the circulating fluidpassage to cause the cryogenic liquid to circulate, thereby enablingperpetual cooling of the cooled device.

<Overall Configuration of the Liquid Supply System>

FIG. 1 is a schematic diagram illustrating the overall configuration ofthe liquid supply system, where the overall configuration of the liquidsupply system is illustrated in a cross section. FIG. 1 illustrates theoverall configuration in a cross section in a plane containing thecenter axis.

The liquid supply system 10 includes a main unit of the liquid supplysystem 100 (which will be referred to as the “main system unit 100”hereinafter), a vacuum container 200 in which the main system unit 100is housed, and pipes (including an inlet pipe 310 and an outlet pipe320). The inlet pipe 310 and the outlet pipe 320 both extend into theinterior of the vacuum container 200 from outside the vacuum container200 and are connected to the main system unit 100. The interior of thevacuum container 200 is a hermetically sealed space. The interior spaceof the vacuum container 200 outside the main system unit 100, the inletpipe 310, and the outlet pipe 320 is kept in a vacuum state. Thus, thisspace provides heat insulation. The liquid supply system 10 is normallyinstalled on a horizontal surface. In the installed state, the upwarddirection of the liquid supply system 10 in FIG. 1 is the verticallyupward direction, and the downward direction in FIG. 1 is the verticallydownward direction.

The main system unit 100 includes a linear actuator 110 serving as adriving source, a shaft member 120 that is moved in vertically upwardand downward directions by the linear actuator 110, and a container 130.The linear actuator 110 is fixed on something suitable, which may be thecontainer 130 or something that is not shown in the drawings. Thecontainer 130 includes a first casing 131 and a second casing 132 thatis provided in such a way as to surround the outer wall of the firstcasing 131.

The shaft member 120 extends from outside the container 130 into theinside through an opening 131 a provided in the ceiling portion of thefirst casing 131. The first casing 131 has an inlet 131 b and an outlet131 c for liquid (cryogenic liquid) on its bottom. The aforementionedinlet pipe 310 is connected to the inlet 131 b and the outlet pipe 320is connected to the outlet 131 c.

Inside the first casing 131 are provided a plurality of structuralcomponents that compart the interior space into plurality of spaces,which constitute a plurality of pump chambers, passages for liquid, andvacuum chambers providing heat insulation. In the following, thestructure inside the first casing 131 will be described in furtherdetail.

The shaft member 120 has a main shaft portion 121 having a cavity in it,a cylindrical portion 122 surrounding the outer circumference of themain shaft portion 121, and a connecting portion 123 that connects themain shaft portion 121 and the cylindrical portion 122. The cylindricalportion 122 is provided with an upper outward flange 122 a at its upperend and a lower outward flange 122 b at its lower end.

The first casing 131 has a substantially cylindrical body portion 131Xand a bottom plate 131Y. The body portion 131X has a first inward flange131Xa provided near its vertical center and a second inward flange 131Xbprovided on its upper portion.

Inside the body portion 131X, there are a plurality of first fluidpassages 131Xc that extend in the axial direction below the first inwardflange 131Xa and are spaced apart from one another along thecircumferential direction. Inside the body portion 131X, there also is asecond fluid passage 131Xd, which is an axially extending cylindricalspace provided radially outside the region in which the first fluidpassages 131Xc are provided. The bottom portion of the first casing 131is provided with a fluid passage 131 d that extends circumferentiallyand radially outwardly to join to the first fluid passages 131Xc.Furthermore, the bottom plate 131Y of the first casing 131 is providedwith a fluid passage 131 e that extends circumferentially and radiallyoutwardly. These fluid passages 131 d and 131 e extend uniformly allalong the circumferential direction to allow liquid to flow radiallyoutwardly in all directions, namely 360 degrees about the center axis.

Inside the container 130, there are provided a first bellows 141 and asecond bellows 142, which expand and contract with the up and downmotion of the shaft member 120. The first bellows 141 and the secondbellows 142 are arranged one above the other along the verticaldirection. The upper end of the first bellows 141 is fixedly attached tothe upper outward flange 122 a of the cylindrical portion 122 of theshaft member 120, and the lower end of the first bellows 141 is fixedlyattached to the first inward flange 131Xa of the first casing 131. Theupper end of the second bellows 142 is fixedly attached to the firstinward flange 131Xa of the first casing 131, and the lower end of thesecond bellows 142 is fixedly attached to the lower outward flange 122 bof the cylindrical portion 122 of the shaft member 120. The spacesurrounding the outer circumference of the first bellows 141 forms afirst pump chamber P1, and the space surrounding the outer circumferenceof the second bellows 142 forms a second pump chamber P2.

Inside the container 130, there also are provided a third bellows 151and a fourth bellows 152, which expand and contract with the up and downmotion of the shaft member 120. The upper end of the third bellows 151is fixedly attached to the ceiling portion of the first casing 131, andthe lower end of the third bellows 151 is fixedly attached to the shaftmember 120. Thus, the opening 131 a of the first casing 131 is closed.The upper end of the fourth bellows 152 is fixedly attached to thesecond inward flange 131Xb provided on the first casing 131, and thelower end of the fourth bellows 152 is fixedly attached to theconnecting portion 123 of the shaft member 120.

A first space K1 is formed by the cavity in the main shaft portion 121of the shaft member 120. A second space K2 is formed outside the thirdbellows 151 and inside the fourth bellows 152. A third space K3 isformed inside the first bellows 141 and the second bellows 142. Thefirst space K1, the second space K2, and the third space K3 are incommunication with each other.

Inside the first casing 131, there are a fluid passage passing throughthe first pump chamber P1 and a fluid passage passing through the secondpump chamber P2. The second casing 132 is configured to surround theouter wall of the first casing 131. An annular fourth space K4 is formedbetween the first casing 131 and the second casing 132. The fourth spaceK4 may also be in communication with the first space K1, the secondspace K2, and the third space K3. The space constituted by the first tofourth spaces K1, K2, K3, and K4 is configured to be capable of beinghermetically sealed.

There are four check valves 160 including a first check valve 160A, asecond check valve 160B, a third check valve 160C, and a fourth checkvalve 160D, which are provided at different locations inside thecontainer 130. Each of these check valves 160 is an annular componentprovided coaxially with the shaft member 120. Each of the check valves160 is configured to allow flow of liquid in radial directions frominside to outside and to block flow of liquid in radial directions fromoutside to inside.

The first check valve 160A and the third check valve 160C are providedin the fluid passage passing through the first pump chamber P1. Thefirst check valve 160A and the third check valve 160C function to blockbackflow of liquid pumped by the pumping effect of the first pumpchamber P1. Specifically, the first check valve 160A is provided on theupstream side of the first pump chamber P1, and the third check valve160C is provided on the downstream side of the first pump chamber P1.More specifically, the first check valve 160A is provided in the fluidpassage 131 d provided in the bottom portion of the first casing 131.The third check valve 160C is provided in the fluid passage formed inthe vicinity of the second inward flange 131Xb provided on the firstcasing 131.

The second check valve 160B and the fourth check valve 160D are providedin the fluid passage passing through the second pump chamber P2. Thesecond check valve 160B and the fourth check valve 160D function toblock backflow of liquid pumped by the pumping effect of the second pumpchamber P2. Specifically, the second check valve 160B is provided on theupstream side of the second pump chamber P2, and the fourth check valve160D is provided on the downstream side of the second pump chamber P2.More specifically, the second check valve 160B is provided in the fluidpassage 131 e provided in the bottom plate 131Y of the first casing 131.The fourth check valve 160D is provided in the fluid passage formed inthe vicinity of the first inward flange 131Xa of the first casing 131.

<Description of the Overall Operation of the Liquid Supply System>

The overall operation of the liquid supply system will be described.When the shaft member 120 is lowered by the linear actuator 110, thefirst bellows 141 contracts, and the second bellows 142 expands.Consequently, the fluid pressure in the first pump chamber P1 decreases.Then, the first check valve 160A is opened, and the third check valve160C is closed. In consequence, liquid supplied from outside the liquidsupply system 10 through the inlet pipe 310 (indicated by arrow S10) istaken into the interior of the container 130 through the inlet 131 b andpasses through the first check valve 160A (indicated by arrow S11).Then, the liquid having passed through the first check valve 160A ispumped into the first pump chamber P1 through the first fluid passage131Xc in the body portion 131X of the first casing 131. On the otherhand, the fluid pressure in the second pump chamber P2 increases. Then,the second check valve 160B is closed, and the fourth check valve 160Dis opened. In consequence, the liquid in the second pump chamber P2 ispumped into the second fluid passage 131Xd provided in the body portion131X through the fourth check valve 160D (see arrow T12). Then, theliquid passes through the outlet 131 c and is brought to the outside ofthe liquid supply system 10 through the outlet pipe 320.

When the shaft member 120 is raised by the linear actuator 110, thefirst bellows 141 expands, and the second bellows 142 contracts.Consequently, the fluid pressure in the first pump chamber P1 increases.Then, the first check valve 160A is closed, and the third check valve160C is opened. In consequence, the liquid in the first pump chamber P1is pumped into the second fluid passage 131Xd provided in the bodyportion 131X through the third check valve 160C (indicated by arrowT11). Then, the liquid passes through the outlet 131 c and is brought tothe outside of the liquid supply system 10 through the outlet pipe 320.On the other hand, the fluid pressure in the second pump chamber P2decreases. Then, the second check valve 160B is opened, and the fourthcheck valve 160D is closed. In consequence, liquid supplied from outsidethe liquid supply system 10 through the inlet pipe 310 (indicated byarrow S10) is taken into the interior of the container 130 through theinlet 131 b and passes through the second check valve 160B (indicated byarrow S12). Then, the liquid having passed through the second checkvalve 160B is pumped into the second pump chamber P2.

As above, the liquid supply system 10 can cause liquid to flow from theinlet pipe 310 to the outlet pipe 320 both when the shaft member 120moves downward and when the shaft member 120 moves upward. Hence, thephenomenon called pulsation can be reduced.

<Precooling>

Now, precooling will be described. As described in the description ofthe background art, in order to cause cryogenic liquid to circulate whenthe system is started for the first time or when the system is startedafter maintenance, it is necessary to precool the container entirely soas to prevent the cryogenic liquid from evaporating in the fluidpassage. In this embodiment, cryogenic liquid is caused to flow in thefourth space K4 formed between the first casing 131 and the secondcasing 132 before cryogenic liquid is supplied to the fluid passagespassing through the pump chambers (the first pump chamber P1 and thesecond pump chamber P2). In the following, the process of precoolingwill be specifically described.

To the fourth space K4 are connected a first pipe 410 for deliveringliquid for precooling and a second pipe 420 for discharging the liquidfor precooling. The first pipe 410 and the second pipe 420 are indicatedby broken lines in FIG. 1, because they are provided at locationsoutside the cross section shown in FIG. 1. When precooling is performed,the fourth space K4, the vacuum container 200, and the fluid passagefrom the inlet pipe 310 to the outlet pipe 320 are evacuated firstly,and then a gas having a boiling point lower than the temperature of thecryogenic liquid for precooling is supplied into the fourth space K4 andthe fluid passage from the inlet pipe 310 to the outlet pipe 320. Afterthe fourth space K4 and the fluid passage from the inlet pipe 310 to theoutlet pipe 320 are filled with the gas, the cryogenic liquid issupplied into the fourth space K4 through the first pipe 410. At thattime, the second pipe 420 is opened to discharge the gas from the fourthspace K4.

After the container 130 is cooled, the cryogenic liquid is dischargedthrough the second pipe 420 by a discharging pump (e.g. dry-sealedvacuum pump), which is not illustrated in the drawings. The cryogenicliquid is discharged to the atmosphere after vaporized and passingthrough a heat exchanger, where it is heated to a temperature near roomtemperature. A chamber capable of storing the cryogenic liquid may beprovided in the discharging fluid passage downstream of the heatexchanger to prevent the cryogenic liquid from being discharged to theatmosphere in the liquid state. A pressure relief valve may be providedto prevent the fluid pressure in the discharging fluid passage frombecoming excessively high.

As above, after the fourth space K4 is cooled, the cryogenic liquid isdischarged, and hence the fourth space K4 is in a vacuum state. Thefirst space K1, the second space K2, and the third space K3 may be incommunication with the fourth space K4, as described above. If this isthe case, the first space K1, the second space K2, and the third spaceK3 are also in a vacuum state after cooled by the above-describedprecooling process.

By cooling the fourth space K4 (and the first space K1, the second spaceK2, and the third space K3 also in this embodiment), the fluid passagepassing through the first pump chamber P1 and the fluid passage passingthrough the second pump chamber P2 are cooled. In consequence, whencryogenic liquid is supplied to these fluid passages, vaporization ofthe cryogenic liquid is prevented from occurring. As the cryogenicliquid flows in these fluid passages, they are cooled in a short time.Thus, the time taken until the pump is started to operate can beshortened. The cryogenic liquid in the fourth space K4 may be dischargedfrom it to evacuate the fourth space K4 after the operation of the pumpis started (in other words, after the up and down motion of the shaftmember caused by the linear actuator 110 is started).

<Advantages of the Liquid Supply System According to this Embodiment>

The liquid supply system 10 can cool the fluid passages in the firstcasing 131 beforehand by causing cryogenic liquid for precooling to flowin the space (the fourth space K4) between the first casing 131 and thesecond casing 132. Thereafter, the fluid passages can be cooled in ashort time by supplying cryogenic liquid to them. Therefore, the timetaken until the pump is started to operate can be shortened.

The liquid supply system is configured to remove cryogenic liquid fromthe fourth space K4 after precooling to keep the fourth space K4 in avacuum state. Therefore, the fourth space K4 can provide heatinsulation.

The liquid supply system has hermetically sealed spaces (the first,second, and third spaces K1, K2, K3) in the first casing 131 that areseparated from the fluid passages passing through the first pump chamberP1 and the second pump chamber P2. These hermetically sealed spaces arein communication with the fourth space K4. Hence, the first space K1,the second space K2, and the third space K3 are also cooled by theprecooling process. This improves the reliability of cooling of thefluid passages passing through the first pump chamber P1 and the secondpump chamber P2. Moreover, the first space K1, the second space K2, andthe third space K3 can also provide heat insulation.

Second Embodiment

FIG. 2 illustrates a liquid supply system in a second embodiment. Thesystem in the first embodiment has a second casing that surrounds theouter wall of the first casing. The system has a third casing thatsurrounds the second casing. The structure and the operation of thesystem are the same as those of the system in the first embodimentexcept for the third casing, and the same components will be denoted bythe same reference signs and will not be described further for the sakeof convenience.

FIG. 2 is a schematic diagram illustrating the overall configuration ofthe liquid supply system, where the overall configuration of the liquidsupply system is illustrated in a cross section. FIG. 2 illustrates theoverall configuration in a cross section in a plane containing thecenter axis. The liquid supply system 10 differs from the system in thefirst embodiment only in the features relating to the third casing 133.The other features are the same as those in the liquid supply system 10in the first embodiment, and the same features will not be describedfurther for the sake of convenience.

The container 130 includes the first casing 131, the second casing 132that surrounds the outer wall of the first casing 131, and the thirdcasing 133 that surrounds the second casing 132. As in the firstembodiment, a fluid passage passing through the first pump chamber P1and a fluid passage passing through the second pump chamber P2 areprovided in the first casing 131. The second casing 132 surrounds theouter wall of the first casing 131. Between the first casing 131 and thesecond casing 132 is the annular fourth space K4. The fourth space K4may be in communication with the first space K1, the second space K2,and the third space K3. The space constituted by the first space K1, thesecond space K2, the third space K3, and the fourth space K4 can behermetically sealed.

The third casing 133 surrounds the outer wall of the second casing 132.The ceiling portion of the third casing 133 covers the ceiling portionof the first casing 131 and the ceiling portion of the second casing 132with a gap between. The ceiling portion of the third casing 133 has anopening 133 a. The shaft member 120 extends into the interior of thecontainer 130 from outside through the opening 133 a. A fifth bellows153 is provided on the upper portion of the third casing 133. The fifthbellows 153 extends and contracts with the up and down motion of theshaft member 120. The upper end of the fifth bellows 153 is fixedlyattached to the shaft member 120, and the lower end of the fifth bellows153 is fixedly attached to the third casing 133. Thus, the opening 133 ais closed.

The third casing 133 configured as above forms a hermetically sealedspace (i.e. the fifth space K5) between the second casing 132 and thethird casing 133. The fifth space K5 is configured to be kept in avacuum state. Hence, the fifth space K5 provides heat insulation.

The overall operation of the liquid supply system and the process ofprecooling are the same as those in the first embodiment and will not bedescribed.

The liquid supply system 10 can also provide advantageous effects thesame as the system in the first embodiment. The fifth space K5 providesheat insulation. This improves the efficiency of cooling of the fourthspace K4 etc. in the precooling process. Moreover, this can preventfreezing from occurring due to thermal contact of the space used forprecooling with something of high temperature (e.g. atmosphere).Specifically, since the top of the ceiling portion of the first casing131 and the ceiling portion of the second casing 132 is covered with thefifth space K5, which provide heat insulation, freezing can be preventedfrom occurring near the ceiling portion of the first casing 131 and theceiling portion of the second casing 132 during precooling.

Others

In the systems in the first and second embodiments, the second pipe 420used for precooling may extend into the interior of the fourth space K4and the orifice of the second pipe 420 may be located in the upperportion of the fourth space K4. This can eliminate difficulties infilling the fourth space K4 with cryogenic liquid that may be involvedin the precooling process due to residence of gas in the upper portionof the fourth space K4.

REFERENCE SIGNS LIST

-   10: liquid supply system-   100: main system unit-   110: linear actuator-   120: shaft member-   121: main shaft portion-   122: cylindrical portion-   122 a: upper outward flange-   122 b: lower outward flange-   123: connecting portion-   130: container-   131: first casing-   131 a: opening-   131 b: inlet-   131 c: outlet-   131 d: fluid passage-   131 e: fluid passage-   131X: body portion-   131Xa: first inward flange-   131Xb: second inward flange-   131Xc: first fluid passage-   131Xd: second fluid passage-   132: second casing-   133: third casing-   133 a: opening-   141: first bellows-   142: second bellows-   151: third bellows-   152: fourth bellows-   153: fifth bellows-   160: check valve-   160A: first check valve-   1606: second check valve-   160C: third check valve-   160D: fourth check valve-   200: vacuum container-   310: inlet pipe-   320: outlet pipe-   410: first pipe-   420: second pipe-   P1: first pump chamber-   P2: second pump chamber

1. A liquid supply system comprising: a container having an inlet and an outlet for cryogenic liquid and provided with a pump chamber inside it; a shaft member that moves vertically upward and downward in the container; and a bellows that expands and contracts with upward and downward motion of the shaft member; wherein the pump chamber is formed by a space surrounding the outer circumference of the bellows, the container includes a first casing in which a fluid passage passing through the pump chamber is provided and a second casing configured in such a way as to surround the outer wall of the first casing, and a space between the first casing and the second casing is configured to allow cryogenic liquid for precooling to flow through it.
 2. The liquid supply system according to claim 1, wherein the space between the first casing and the second casing is kept in a vacuum state with the cryogenic liquid having been removed from the space between the first casing and the second casing after precooling.
 3. The liquid supply system according to claim 1, wherein a hermetically sealed space other than the passage passing through the pump chamber is provided in the interior of the first casing, and the hermetically sealed space and the space between the first casing and the second casing are in communication with each other.
 4. The liquid supply system according to claim 1, further comprising a third casing that surrounds the second casing, wherein a hermetically sealed space kept in a vacuum state is formed between the second casing and the third casing. 